In the design of known non-modular robotic systems, the type of loading (tension, compression, bending and torsion) on each actuator (or joint) can be estimated based on the configuration of the robot which is fixed. The designer normally works backwards incrementally from the end-effector to the base joint, by assuming a worst case configuration of the robot for each joint, to calculate the power/torque required based on the pattern of loading that will be imposed on that joint by the payload of the robot and all joints and links between this joint and the payload. Based on such computations, the non-modular robotic system would be designed as an integral (indivisible) system so that the user will not be able to reconfigure or change the structure without major re-design of the system.
In a modular robotic system, the joints can be arranged, or configured, differently. As a result, there are multiple possible robot structures for the same number of modular joints. Based on the task to be accomplished by a modular robotic system, the user would interconnect certain number of modules to form a desired system. The system may consist of one or more mechanisms (robotic arms, or manipulators). Then, the user would connect the control system to program the motion and actions in accordance with the task specification. The motion may include point-to-point motion, or trajectory tracking motion. The actions may include end-effector control, interfacing to other systems such as tools, machines and the like.
Prior modular robotic systems have several major limitations both in terms of mechanics and electronic control systems controlling the robot. Firstly, the modules have a fixed structure, so that they are permanently configured as either "roll" modules, or "pitch" modules, or "yaw" joints. This is a major limitation for the user when there is a need for the same module to be configured as a "roll" or "pitch" or "yaw" module depending on the task requirements. The modules have no built-in electronics and processors. Further, these modules are configured in such a way that the modules proximal to the manipulator base contain much more wiring than the distal ones so that in general the modules are not mutually exchangeable. In other words, a module designed to be "module #4" in a chain of 6 modules, can not be used as a module #3 since it has no built-in wiring system to support signal transmission to the robot controller. The controller is centralized and connected to the base module through a thick multi-conductor cable system. Therefore a system assembled from such modules, in addition to being modular only in a very limited mechanical sense, is not reconfigurable. In addition, the control system electronics is centralized so that the modules cannot be considered as "intelligent" units taken alone since they lack dedicated control processors and associated software.
It would be very advantageous to provide a self-contained, reconfigurable modular robot joint which can be easily and rapidly assembled to provide several types of joint movement. It would also be advantageous to provide a modular joint which can be easily cascaded to other modular drive joints to build up an integrated robotic or automated system with each joint under overall control by a host controller.